Prior to the present invention, procedures for electrocoating metallic substrates with polymeric organic materials was well established as shown by Basso et al., U.S. Pat. No. 4,038,232, involving electrodeposition of solubilized electrodepositable compositions, for example, epoxy containing organic resins, or Jones, U.S. Pat. No. 4,040,924, relating to the cationic electrodeposition of epoxy resins onto a metallic substrate.
Efforts were made to effect the polymerization of various cationically polymerizable organic materials through electroinitiation to eliminate the requirements of preparing electrodepositable organic polymers, for example, W. Strobel and R. C. Schultz, Die Macromol. Chem., 133, 303 (1970), attempted unsuccessfully to polymerize epoxy monomers employing a 3% LiClO.sub.3 in nitromethane as the electrolyte. Additional studies of electroinitiation of cationic polymerization were performed by B. L. Funt et al., J. Polym. Sci., Pt. A-1, 9, 115 (1971) and P. Cerrai et al., Eur. Polym. J., 15, 153 (1979).
The present invention is based on the discovery that an arylonium salt, as defined hereinafter, can be used to electroinitiate the cationic polymerization of a cationically polymerizable monomer, for example, 4-vinylcyclohexenedioxide. As a result, the coating of a conducting substrate used as the anode can be achieved with a cationically polymerizable organic monomer as the principal component in the electrolyzed bath. Accordingly, electrocoating baths having specially formulated electrodepositable polymers used in the prior art are no longer necessary.